It is necessary for the precise control of an electrical drive to always detect the position of the revolving rotor with absolute accuracy and to know the absolute rotor position already at the start of a rotary movement, in particular in connection with synchronous motors. Various rotatory measuring systems are known for this, which transmit the detected measured position values over respectively several connecting lines to a subordinated evaluation unit, or respectively an electronic follow-up device. In turn, the evaluation unit takes over the drive control as well as further control function, if required. The least possible outlay in respect to the measuring systems used in this is desired.
However, relatively elaborate systems are the result of the employment of highly accurate absolute measuring systems, which possibly also provide incremental data, or of incremental measuring systems also providing absolute commutation signals and whose data are transferred to the evaluation unit. The parallel transmission of absolute and incremental position data, as well as of the reference marker signals, if required, requires a large number of connecting lines.
To reduce the number of required connecting lines between the respective measuring systems and the subordinated evaluation unit, the transmission of the measured values and other data by means of a multiplex operation over as few as possible signal connections is known, for example.